Dr Dawn Harper, spokeswoman for ColdZyme Mouth Spray, said: "More grandparents are providing regular child care for their grandchildren as both parents have work commitments.

"Many of my patients who provide such care tell me it's a job they love, but one that often leaves them feeling exhausted. Fatigue can suppress the immune system, so it's important grandparents get a good night's sleep.

"My parents tell me 'grandparenting' is their favourite hobby.

"They are lucky they are both in good health with robust immune systems, but some grandparents are missing out on such magical moments."

To help grandparents avoid falling ill, Dr Harper recommends regularly washing hands, along with surfaces and door handles, eating a well-balanced diet and making sure you have a good sleep routine.

Grandma Jackie Palmer, of Esher, Surrey, looks after her granddaughter twice a week and says she has caught a cold a number of times after doing so.

The 66-year-old said: "I look after my three-year-old granddaughter twice a week so my daughter can work full time.

"I cherish the time with her but it doesn't come without catching the odd cold, as she picks up germs and viruses from nursery roughly every six weeks.

"I work the rest of the week and having a cold can take its toll, nevertheless, helping my daughter and spending time with my granddaughter is my priority despite the risks."